The invention relates to a chain wheel with a wheel body consisting of a wheel rim and a wheel hub, which wheel body carries a transmitter ring with radially projecting shoulders for detecting various angles of rotation or ranges of angles of rotation.
In order to enable performing controls which depend on the angle of rotation or range of angle of rotation of a chain wheel, the wheel body of the chain wheel is connected with a transmitter ring which is provided with radially projecting shoulders for the contactless (e.g. electromagnetic) detection of the angle or rotation or ranges of angles of rotation as determined by said shoulders. The transmitter ring is placed on the wheel hub of the chain wheel and is caulked with the hub, so that the shoulders project in a radially outwardly fashion into the scanning range of a respective sensor. Since the measurement precision of angle-of-rotation transducers with such transmitter rings which are arranged as stamped parts depends, among other things, on the surface evenness of the transmitter ring, a sufficient stiffness and thus a respective thickness of the transmitter ring is required in order to avoid having to cope with any distortions and thus measurement errors due to axial run-out, which shoulders should have a respective distance from the rotational shaft of the wheel body for reasons of the measurement precision. Notice must further be taken in this connection that due to the demand for the lowest possible weight, the shoulders which extend over a larger angle at circumference are supported by radial arms of the transmitter ring which contributes to the tendency towards distortions in the zone of the shoulders.
The invention is thus based on the object of providing a chain wheel of the kind mentioned above in such a way that, on the one hand, narrow run-out tolerances can be ensured and, on the other hand, savings in weight are enabled.
This object is achieved by the invention in such a way that the transmitter ring provided with inwardly projecting shoulders can be inserted into the wheel rim and can be attached to supports which are distributed over the inner circumference of the wheel ring and form an axial support for the transmitter ring.
Since the shoulders of the transmitter ring which cooperate with the sensor should be provided with a respective radial distance from the rotaional shaft of the wheel body due to the desired measurement precision, the supports which project inwardly in this case can be disposed with a comparably low radial projecting length in the case of a transmitter ring which is not associated with the hub but with the wheel rim, which in connection with a ring attachment not over the circumference but over the face side of the transmitter ring reduces the requirements placed on the torsional stiffness which is necessary for the run-out tolerance, so that the thickness of the transmitter ring can be reduced accordingly, e.g. it can be halved. In this way it is not only possible to ensure the desired reduction in weight, but it is also possible to ensure the reduction of the balance error caused by the transmitter ring. The face-sided axial support of the transmitter ring is provided in a simple manner on respective supports of the wheel body, so that the transmitter ring merely needs to be axially inserted into the wheel rim until it rests on the supports and then needs to connected with the supports.
Since the usual chain wheels are provided with wheel spokes between the hub and the wheel rim, particularly simple constructional conditions are obtained for such chain wheels when the supports are provided in the neck zone of the spokes on the wheel rim. In this case, the supports can be formed by a machining neck on the wheel spokes which hardly increases the weight of the wheel body. The supporting forces are absorbed in any case by the wheel spokes.
The transmitter ring can be glued tightly to the supports. Particularly favorable fastening conditions are obtained, however, when the transmitter ring can be attached to the supports by spot welding. In this case the supports form respective welding projections.